Low volume showerhead with porous baffle

ABSTRACT

A low volume showerhead in a semiconductor processing apparatus can include a porous baffle to improve the flow uniformity and purge time during atomic layer deposition. The showerhead can include a plenum volume, one or more gas inlets in fluid communication with the plenum volume, a faceplate including a plurality of first through-holes for distributing gas onto a substrate in the semiconductor processing apparatus, and a porous baffle positioned in a region between the plenum volume and the one or more gas inlets. The one or more gas inlets can include a stem having a small volume to improve purge time. The baffle can be porous and positioned between the stem and the plenum volume to improve flow uniformity and avoid jetting.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent Application No. 61/988,834, filed May 5, 2014, and titled “ULTRA LOW VOLUME SHOWERHEAD FOR ATOMIC LAYER DEPOSITION,” which is incorporated by reference herein in its entirety and for all purposes.

INTRODUCTION

Field of the Invention

This disclosure generally relates to showerheads for distributing gas in semiconductor processing apparatuses. Certain aspects of this disclosure pertain to a low volume showerhead with a porous baffle for distributing gas in atomic layer deposition processes.

Background

Semiconductor processing tools often include components designed to distribute process gases in a relatively even manner across a semiconductor substrate or wafer. Such components are commonly referred to in the industry as “showerheads.” Showerheads typically include a faceplate that fronts a plenum volume of some sort. The faceplate may include a plurality of through-holes that allow gas in the plenum volume to flow through the faceplate and into a reaction space between the substrate and the faceplate (or between a wafer support supporting the wafer and the faceplate). The through-holes are typically arranged such that the gas distribution across the wafer results in substantially uniform substrate processing.

SUMMARY

This disclosure pertains to a showerhead for use in a semiconductor processing apparatus. The showerhead includes a plenum volume having a first surface and a second surface opposite the first surface, the first surface and the second surface at least partially defining the plenum volume of the showerhead. The showerhead also includes one or more gas inlets in fluid communication with the plenum volume, a faceplate including a plurality of first through-holes, and a baffle including a plurality of second through-holes. The plurality of first through-holes extend from a first side to a second side of the faceplate, where the first side of the faceplate defines the first surface of the plenum volume. The baffle includes a plurality of second through-holes, where the baffle is positioned in a region between the plenum volume and the one or more gas inlets.

In some implementations, a diameter of the faceplate is at least four times greater than a diameter of the baffle. In some implementations, a volume of the showerhead is between about 50 milliliters and about 500 milliliters. In some implementations, a porosity of the baffle is between about 5% and about 25%. In some implementations, the plurality of second through-holes are positioned more towards the edges of the baffle than the center of the baffle. In some implementations, the showerhead further includes a backplate opposite the faceplate, where a side of the backplate defines the second surface of the plenum volume, and where the region between the plenum volume and the one or more gas inlets is recessed into the side of the backplate defining the second surface of the plenum volume.

This disclosure also pertains to a semiconductor processing station including the aforementioned showerhead. The semiconductor processing station includes a controller configured with instructions to perform the following operations: providing a substrate into the semiconductor processing station, introducing reactant gas into the semiconductor processing station through the showerhead to adsorb onto the surface of the substrate, introducing a purge gas into the semiconductor processing station through the showerhead, and applying a plasma to form a thin film layer from the adsorbed reactant gas on the surface of the substrate.

In some implementations, a film non-uniformity of the thin film layer is less than about 0.5%. In some implementations, the film non-uniformity is decoupled from one or more process parameters associated with one or more of introducing the gas reactant, introducing the purge gas, and applying the plasma. In some implementations, forming the thin film layer in an atomic layer deposition (ALD) cycle is performed in less than about 1.5 seconds.

This disclosure also pertains to a semiconductor processing tool including the aforementioned semiconductor processing station. In some implementations, the semiconductor processing tool includes a stepper.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an isometric section view of an example showerhead with a baffle.

FIG. 2 shows an isometric section view of an example low volume showerhead with a porous baffle.

FIG. 3 shows a magnified isometric section view of the porous baffle in the low volume showerhead of FIG. 2.

FIG. 4A and FIG. 4B show a side-by-side comparison of side section views of two example showerheads.

FIG. 5 shows an example layout of an arrangement of through-holes for a faceplate and a porous baffle in a low volume showerhead.

FIG. 6A shows a side section view of a portion of an example showerhead including a baffle with arrows indicating nominal gas flow directions within the showerhead.

FIG. 6B shows a side section view of a portion of an example low volume showerhead including a porous baffle with arrows indicating nominal gas flow directions within the low volume showerhead.

FIG. 7A shows an isometric view of an example baffle in a showerhead.

FIG. 7B shows an isometric view of an example baffle including a plurality of through-holes in a showerhead.

FIG. 8 shows a graph depicting axial flow velocity of gas from a faceplate of a showerhead as a function of a radial dimension of the faceplate.

FIG. 9 shows a graph depicting a percentage of non-uniformity of atomic layer deposition for two showerheads.

FIG. 10 shows a schematic view of a multi-station processing tool that may include a low volume showerhead with a porous baffle.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the presented concepts. The presented concepts may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail so as to not unnecessarily obscure the described concepts. While some concepts will be described in conjunction with the specific embodiments, it will be understood that these embodiments are not intended to be limiting.

In this application, the terms “semiconductor wafer,” “wafer,” “substrate,” “wafer substrate,” and “partially fabricated integrated circuit” are used interchangeably. One of ordinary skill in the art would understand that the term “partially fabricated integrated circuit” can refer to a silicon wafer during any of many stages of integrated circuit fabrication thereon. A wafer or substrate used in the semiconductor device industry typically has a diameter of 200 mm, or 300 mm, or 450 mm. The following detailed description assumes the invention is implemented on a wafer. However, the invention is not so limited. The work piece may be of various shapes, sizes, and materials. In addition to semiconductor wafers, other work pieces that may take advantage of this invention include various articles such as printed circuit boards, magnetic recording media, magnetic recording sensors, mirrors, optical elements, micro-mechanical devices and the like.

Several conventions may have been adopted in some of the drawings and discussions in this disclosure. For example, reference is made at various points to “volumes,” e.g., “plenum volumes.” These volumes may be generally indicated in various Figures, but it is understood that the Figures and the accompanying numerical identifiers represent an approximation of such volumes, and that the actual volumes may extend, for example, to various solid surfaces that bound the volumes. Various smaller volumes, e.g., gas inlets or other holes leading through an otherwise solid boundary surface of a plenum volume, may be fluidly connected to plenum volumes.

It is to be understood that the use of relative terms such as “above,” “on top,” “below,” “underneath,” etc. are to be understood to refer to spatial relationships of components with respect to the orientations of those components during normal use of a showerhead. In other words, the showerhead can be oriented so as to distribute gases downwards towards a substrate during substrate processing operations.

Introduction

Among various deposition techniques used in semiconductor processing, one particular deposition technique can include atomic layer deposition (ALD). In contrast with a chemical vapor deposition (CVD) process, where thermally activated gas phase reactions are used to deposit films, ALD processes use surface-mediated deposition reactions to deposit films on a layer-by-layer basis. In one example ALD process, a substrate surface, including a population of surface active sites, is exposed to a gas phase distribution of a first film precursor (P1). Some molecules of P1 may form a condensed phase atop the substrate surface, including chemisorbed species and physisorbed molecules of P1. The reactor is then evacuated to remove gas phase and physisorbed P1 so that only chemisorbed species remain. A second film precursor (P2) is then introduced to the reactor so that some molecules of P2 adsorb to the substrate surface. The reactor may again be evacuated, this time to remove unbound P2. Subsequently, energy provided to the substrate activates surface reactions between adsorbed molecules of P1 and P2, forming a film layer. Finally, the reactor is evacuated to remove reaction by-products and possibly unreacted P1 and P2, ending the ALD cycle. Additional ALD cycles may be included to build film thickness.

Depending on the exposure time of the precursor dosing steps and the sticking coefficients of the precursors, each ALD cycle may deposit a film layer of, in one example, between one-half and three angstroms thick. Each ALD cycle can last about 5 seconds or less, about 3 seconds or less, or about 2 seconds or less.

Conformal film deposition (CFD) is a deposition technique that is similar to ALD techniques in that deposition is performed over multiple cycles, with each cycle employing a small amount of reactant or precursor. Typically, the surface reaction to produce a CFD film is activated by exposure of the surface-adsorbed reactant(s) to a plasma, ultraviolet radiation, or similar source. In some cases, one reactant flows continuously during the deposition process, which may include several cycles of CFD. Unlike ALD processes, many CFD processes may allow two or more reactants to co-exist in the vapor phase within a chamber. In CFD, one or more process steps described in an ALD process may be shortened or eliminated in an example CFD process. Methods for forming films using CFD are described in U.S. patent application Ser. No. 13/084,399, filed on Apr. 11, 2011, and which is incorporated by reference herein for all purposes. For context, a short description of CFD is provided.

Generally, a CFD cycle is the minimum set of operations that may be performed for a surface deposition reaction. The result of one cycle is production of at least a partial thin film layer on a substrate surface. Typically, a CFD cycle will include only those steps necessary to deliver and adsorb each reactant to the substrate surface, and then react those adsorbed reactants to form the partial layer of film. Of course, the cycle may include certain ancillary steps such as sweeping one or more of the reactants or byproducts and/or treating the partial film as deposited. Generally, a cycle contains only one instance of a unique sequence of operations. As an example, a cycle may include the following operations: (i) delivery/adsorption of reactant A, (ii) delivery/adsorption of reactant B, (iii) sweep B out of the reaction chamber using a purge gas, and (iv) apply plasma to drive a surface reaction of A and B to form the partial film layer on the surface. In some implementations, these steps can be characterized as a dose step, a purge step, and a plasma step. In some implementations, a post-plasma purge step may be included in the cycle for further purging.

Some implementations may use different process sequences. One possible process includes the following sequence of operations: (1) flow auxiliary reactant continuously, (2) provide dose of silicon-containing or other principle reactant, (3) purge 1, (4) expose substrate to RF plasma, (5) purge 2. Another alternative process includes the following sequence of operations: (1) flow inert gas continuously, (2) provide dose of silicon-containing or other principle reactant, (3) purge 1, (4) expose substrate to RF plasma while providing dose of oxidant or other auxiliary reactant, (5) purge 2.

Generally, a concept of a “sweep” or “purge” phase removes or purges one of the vapor phase reactant from a reaction chamber and typically occurs only after delivery of such reactant is completed. In other words, that reactant is no longer delivered to the reaction chamber during the purge phase. However, the reactant remains adsorbed on the substrate surface during the purge phase. Typically, the purge serves to remove any residual vapor phase reactant in the chamber after the reactant is adsorbed on the substrate surface to the desired level. A purge phase may also remove weakly adsorbed species (e.g., certain precursor ligands or reaction by-products) from the substrate surface.

In semiconductor processing equipment, a showerhead is often used to distribute process gases across a semiconductor substrate in a desired manner, such as in an evenly distributed manner. Showerheads typically include a plenum that is bounded by a faceplate with a plurality of gas distribution holes that lead to the outside of the showerhead. The faceplate typically faces a substrate reaction area within a semiconductor processing chamber or reaction chamber, and substrates are usually placed beneath the faceplate within the semiconductor processing chamber, such as on a wafer support or pedestal that supports the wafer in a location below the faceplate.

Thin films are grown on a substrate surface in a self-limiting and self-saturating manner in ALD. In other words, precursors are delivered and react with the surface in a self-limiting way such that the reaction terminates once all the reactive sites on the surface are consumed. This means that a particular step in the ALD process has reached saturation. Typically, film uniformity is not an issue when full saturation is reached. However, many ALD processes operate more economically and desire a certain threshold of throughput. As a result, not all of the steps in ALD reach full saturation to achieve a desired throughput, so full saturation in ALD processes may be throughput-prohibitive. By way of an example, an ALD process may reach between about 70% and about 99% saturation to achieve a desired throughput. As used herein, ALD processes can include CFD processes and may be used interchangeably.

Thus, a higher throughput can be achieved at the expense of film uniformity, and greater film uniformity can be achieved at the expense of throughput. However, a showerhead of the present disclosure can be designed to improve film uniformity and throughput. In some implementations, the showerhead can be designed to facilitate the delivery of process or purge gases in ALD processes. In an ALD process, improvements to flow uniformity in delivery of reactants in the vapor phase can improve the uniformity of deposited films, particularly during the dosing and plasma steps. Also, improvements to purge time can improve the efficiency of the purge step, thereby increasing the throughput of the ALD process.

A showerhead that improves throughput can be obtained by reducing the volume of the showerhead. A plenum volume and a stem volume can be lowered or minimized to reduce purge time for completing the purging of precursors during the purge step. The reduced volume increases the backpressure so that purge gas can be quickly and efficiently delivered into a reaction chamber. However, reducing the volume of the showerhead can typically compromise the film uniformity of a deposited film. Obtaining a spatially uniform flow across a faceplate of a showerhead may be difficult in a low volume showerhead. A spatially non-uniform flow across the faceplate can result in thickness non-uniformities in the film being deposited. As noted above, in some ALD processes, a deposition cycle in an ALD process may be short and may not permit full saturation to be reached. Hence, spatially non-uniform flow across the faceplate may adversely affect film uniformity and film properties of deposited films.

Low Volume Showerhead with Porous Baffle

The present disclosure provides a showerhead having a reduced volume without suffering the penalty of spatially non-uniform flow. Such a low volume showerhead can include a porous baffle recessed into a region between a stem volume and a plenum volume. A low volume showerhead can refer to a showerhead having a total volume of about equal to or less than 500 milliliters. In some implementations, a low volume showerhead can have a volume between about 50 milliliters and about 500 milliliters. A conventional showerhead can have a volume greater than 500 milliliters, especially in ALD applications.

In general, there are two main types of showerheads: a chandelier type and a flush mount type. A chandelier type showerhead has a stem attached to the top of the chamber on one end and a faceplate or a backplate on the other end. A part of the stem may protrude from the chamber top for connecting gas lines and RF power. A flush mount showerhead type is integrated into the top of a chamber and typically does not have a stem. While the depicted drawings generally refer to chandelier type showerheads, it should be understood that the present disclosure can apply to flush mount type showerheads as well.

FIG. 1 shows an isometric section view of an example showerhead 100 with a baffle 110. The showerhead 100 in FIG. 1 can have a volume greater than 500 milliliters and include a non-porous baffle 110. As shown in FIG. 1, the showerhead 100 includes a backplate 102 and a faceplate 104, where the backplate 102 and the faceplate 104 may be separate mechanical components or integrated into a single body. The backplate 102 and the faceplate 104 may be positioned opposite one another. The faceplate 104 may have a plurality of gas distribution holes or through-holes 132 to facilitate delivery of gas to a substrate. A plenum volume 130 may be defined between the backplate 102 and the faceplate 104, where the plenum volume 130 can have a first surface and a second surface opposite the first surface. In some implementations, the first surface and the second surface of the plenum volume 130 can have circumferential surfaces. The first surface and the second surface can at least partially define the plenum volume 130 of the showerhead 100. A first side of the faceplate 104 can define the first surface of the plenum volume 130. A second side of the backplate 102 can define the second surface of the plenum volume 130. In some implementations, as illustrated in FIG. 1, the plenum volume 130 can be substantially conical in shape along the second surface of the plenum volume 130.

The plenum volume 130 may be supplied with a gas, such as reactant gas or purge gas, via one or more gas inlets 120. The gas inlet 120 in FIG. 1 may be connected to a gas supply or supplies for delivery of the gas. The gas inlet 120 can include a stem 122, where the stem 122 can include an expanded tube 126 connected to a narrow tube 124. The expanded tube 126 can have a diameter greater than a diameter of the narrow tube 124 to provide a more spatially distributed flow upon reaching the plenum volume 130.

The showerhead 100 can further include a baffle 110 recessed in the plenum volume 130. The baffle 110 may be a solid or non-porous structure mounted in the plenum volume 130 to direct the gas outwardly throughout the plenum volume 130 and towards the edge of the faceplate 104. The baffle 110 may be mounted at a certain distance from the gas inlet 120 to permit distribution of the gas within the plenum volume 130. Furthermore, the plenum volume 130 at the second surface can be conical to provide more space between the gas inlet 120 and the baffle 110. In some implementations, the baffle 110 can be circular and have a diameter greater than a diameter of the expanded tube 124. By directing the flow of gas outwardly throughout the plenum volume 130, greater flow uniformity can be obtained. Moreover, the baffle 110 can be substantially centered on the gas inlet 120 to avoid or otherwise minimize the flow of gas from jetting through the center of the faceplate 104.

FIG. 2 shows an isometric section view of an example low volume showerhead 200 with a porous baffle 210. The porous baffle 210 may also be referred to as a porous baffle plate. The low volume showerhead 200 in FIG. 2 can have a volume between about 50 milliliters and about 500 milliliters and include a porous baffle 210. In some implementations, the low volume showerhead 200 can have a volume between about 100 milliliters and about 300 milliliters. The low volume showerhead 200 includes a backplate 202 and a faceplate 204, where the backplate 202 and the faceplate 204 may be separate mechanical components or integrated into a single body. The backplate 202 and the faceplate 204 may be positioned opposite one another. In some implementations, the backplate 202 and the faceplate 204 may each be cylindrical in shape. The faceplate 204 may have a plurality of through-holes 232 to facilitate delivery of gas to a substrate. In some implementations, the size (e.g., diameter) of the faceplate 204 may correspond or substantially correspond to the size of the substrate being processed. The through-holes 232 may extend through faceplate 204 from a first side to a second side of the faceplate 204. A plenum volume 230 may be defined between the backplate 202 and the faceplate 204, where the plenum volume 230 can have a first surface and a second surface opposite the first surface. In some implementations, the first surface and the second surface of the plenum volume 230 can have circumferential surfaces. The first surface and the second surface can at least partially define the plenum volume 230 of the low volume showerhead 200. A first side of the faceplate 204 can define the first surface of the plenum volume 230. A second side of the backplate 202 can define the second surface of the plenum volume 230. In some implementations, as illustrated in FIG. 2, the plenum volume 230 can be cylindrical or substantially cylindrical in shape. This can reduce the overall internal volume of the showerhead because the plenum volume 230 in FIG. 2 has a reduced volume compared to the plenum volume 130 in FIG. 1.

The plenum volume 230 may be supplied with a gas, such as reactant gas or purge gas, via one or more gas inlets 220. The gas inlet 220 in FIG. 2 may be connected to a gas supply or supplies for delivery of the gas. The gas inlet 220 can include a stem 222, where the stem 222 can include a narrow tube 224. The stem 222 can be in fluid communication with the plenum volume 230. The volume of the stem 222 can be between about 1 milliliter and about 50 milliliters in some implementations. Providing the narrow tube 224 as the entirety of the stem 222 can also reduce the overall internal volume of the showerhead because the narrow tube 224 in FIG. 2 has a smaller diameter than the expanded tube 126 in FIG. 1.

The low volume showerhead 200 can further include a porous baffle 210 in a region 235 between the plenum volume 230 and the gas inlet 220. FIG. 3 shows a magnified isometric section view of the porous baffle 210 in the low volume showerhead 200 of FIG. 2. In some implementations, the porous baffle 210 can be recessed in the region 235, where the porous baffle 210 may be mounted at a certain distance from the gas inlet 220 and above the plenum volume 230. While the porous baffle 210 may be positioned within the region 235, it is understood that the porous baffle 210 may be positioned within the plenum volume 230 in some other implementations. Thus, the porous baffle 210 may be mounted at a distance from the gas inlet 220 that extends through the region 235. The region 235 can be a recessed volume of the backplate 202. The region provides a transition area for the flow of gas between the gas inlet 220 and the plenum volume 230. In some implementations, the region 235 can be recessed into the second side of the backplate 202, where the second side of the backplate 202 defines the second surface of the plenum volume 230. In some implementations, each of the stem 222, the region 235, and the plenum volume 230 define a cylindrical volume, where a diameter of the plenum volume 230 is greater than a diameter of the region 235, and the diameter of the region 235 is greater than a diameter of the stem 222.

While it is understood that the porous baffle 210 may be characterized as positioned in a region 235 between the plenum volume 230 and the gas inlet 220, it should be understood by a person of ordinary skill in the art that the region 235 may be considered as part of the gas inlet 220, and that the porous baffle 210 may be positioned within the gas inlet 220. However, rather than blocking the flow of gas while being positioned in the gas inlet 220, the porous baffle 210 may have a porosity that permits gas to flow through.

The baffle 210 can be selectively porous, where the porosity of the baffle 210 can be between about 5% and about 25%. In some implementations, the baffle 210 can include or otherwise made of a porous material. Examples of porous material can include porous aluminum, porous alumina, and porous quartz. The baffle 210 can be made of any suitable material, including but not limited to aluminum, alumina, quartz, and stainless steel. The material may be compatible with remote cleans and may be material that passivates or does not readily react with ammonia/fluorine radicals. In some implementations, the baffle 210 can include a plurality of through-holes 212 extending through the baffle 210. The through-holes 212 may be provided through a material of the baffle 210 to effectively simulate and mimic porosity. In some implementations, the baffle 210 can be circular and have a diameter greater than a diameter of the stem 222. However, in some implementations, the baffle 210 is substantially smaller than the faceplate 204. For example, a diameter of the faceplate 204 is at least four times greater than a diameter of the baffle plate 210, or at least ten times greater than a diameter of the baffle plate 210. Also, the baffle 210 can have a diameter smaller than the diameter of the region 235. Accordingly, gas flow may be directed not only through the through-holes 212, but also outwardly throughout the plenum volume 230 towards the edges of the faceplate 204. By directing the flow of gas through the through-holes 212 and outwardly throughout the plenum volume 230, a more spatially uniform flow of gas can be obtained despite lowering the overall internal volume of the showerhead 200 compared to the showerhead 100 in FIG. 1. Furthermore, the baffle 210 can be substantially centered on the gas inlet 220 so that the position of the baffle 210 and the porosity of the baffle 210 can minimize the effects of gas jetting through the center of the faceplate 204. In some implementations, the baffle 210 can be substantially parallel to the first surface and the second surface of the plenum volume 230.

FIG. 4A and FIG. 4B show a side-by-side comparison of side section views of two example showerheads 400 a, 400 b. A conventional showerhead 400 a is shown on the left side in FIG. 4A and a low volume showerhead 400 b of the present disclosure is shown on the right side in FIG. 4B. The conventional showerhead 400 a can correspond to the showerhead 100 in FIG. 1, and the low volume showerhead 400 b can correspond to the low volume showerhead 200 in FIG. 2.

Each showerhead 400 a, 400 b includes a backplate 402 and a faceplate 404 opposite the backplate 402. The backplate 402 a and the faceplate 404 a of the conventional showerhead 400 a at least partially define a plenum volume 430 a, where the plenum volume 430 a includes both a cylindrical portion and a conical portion over the cylindrical portion. The backplate 402 b and the faceplate 404 b of the low volume showerhead 400 b at least partially define a plenum volume 430 b, where the plenum volume 430 b includes a cylindrical portion. Each showerhead 400 a, 400 b also includes a stem 422 a, 422 b through which gas is delivered into the plenum volume 430 a, 430 b. The stem 422 a in the conventional showerhead 400 a includes a narrow tube 424 a and an expanded tube 426 a, and the stem 422 b in the low volume showerhead 400 b includes a narrow tube 424 b. Thus, the conventional showerhead 400 a may have a significantly larger volume than the low volume showerhead 400 b because of a larger stem diameter and a larger plenum height. The larger volume in the conventional showerhead 400 a may lead to recirculation zones with respect to the flow of gas in the plenum volume 430 a that can result in flow uniformity drifting. The larger volume in the conventional showerhead 400 a may also lead to longer purge time and increased transient time, resulting in a reduced throughput.

Additionally, the showerheads 400 a, 400 b include baffles 410 a, 410 b, where the conventional showerhead 400 a includes a large, non-porous baffle 410 a and the low volume showerhead 400 b includes a small, porous baffle 410 b. In some implementations, the small, porous baffle 410 b is recessed in a region 435 b between the plenum volume 430 b and the stem 422 b. In some implementations, the region 435 b can constitute an extension of the stem 422 b, where the region 435 b has a larger diameter than the narrow tube 424 b. The small, porous baffle 410 b may be considered to be inside the stem 422 b in such implementations. In some implementations, the region 435 b can serve as a diffuser, where the diffuser can be conical or cylindrical in shape. The small, porous baffle 410 b may increase flux through the center of the faceplate 404 compared to the large, non-porous baffle 410 a. In some implementations, the number of holes and the arrangement of holes in the small, porous baffle 410 b can provide a more spatially uniform flow of gas through the faceplate 404 b. In some implementations, the number and the arrangement of holes in the faceplate 404 b can also affect the spatial uniformity of flow of gas through the faceplate 404 b. For example, a reduced hole count in the faceplate 404 b can increase the pressure drop across the faceplate 404 b to push the flow of gas more outwardly towards the edges of the faceplate 404 b.

Table 1 shows a comparison of features and values between the conventional showerhead 400 a and the low volume showerhead 400 b.

TABLE 1 Conventional Low Volume Feature Showerhead 400a Showerhead 400b Overall internal 742.7 milliliters 256.4 milliliters volume Height 10.55 inches 10.55 inches (stem to faceplate) Faceplate diameter 13 inches 13 inches Plenum shape Conical Cylindrical (sloped back) (parallel back) Plenum height 0.25 inches 0.125 inches (at edge) Hole pattern Hexagonal Triangular Hole count 3292 2257 Hole diameter 0.04 inches 0.04 inches Expansion zone in Yes (1.21 inch diameter) No stem Baffle Solid baffle Porous baffle Baffle diameter 2.13 inches 0.79 inches Baffle through-hole N/A 0.08 inches (6 diameter through-holes) Baffle recessed in No Yes region between stem and plenum? Baffle thickness 0.064 inches 0.04 inches

The low volume showerhead 400 b of the present disclosure can have an overall internal volume less than about 700 milliliters, or between about 50 milliliters and about 500 milliliters, or between about 100 milliliters and about 300 milliliters. In Table 1, the low volume showerhead 400 b of the present disclosure reduces the overall internal volume of the conventional showerhead 400 a from 742.7 milliliters to 256.4 milliliters, which represents a 65% reduction in volume. The plenum height in the conventional showerhead 400 a can be reduced from 0.25 inches to 0.125 inches in the low volume showerhead 400 b. The plenum shape in the conventional showerhead 400 a can be substantially conical, or at least comprise a combination of a substantially conical portion and a substantially cylindrical portion. A cone divergence of the substantially conical portion can be greater than about 90 degrees, or greater than about 120 degrees. The plenum shape in the low volume showerhead 400 b can be cylindrical or substantially cylindrical. The stem diameter in the conventional showerhead 400 a can be reduced from a diameter of 1.21 inches to a diameter of about 0.125 inches and higher in the low volume showerhead 400 b. In some implementations, this can reduce the purge time and improve throughput in semiconductor applications, such as for ALD applications. In some implementations, the stem diameter in the low volume showerhead 400 b can transition from the smaller diameter to a larger diameter in a transition region 435 b, where the larger diameter can be about 1.21 inches or less.

In some implementations, the number of through-holes in the faceplate 404 a, 404 b can influence the uniformity of flow across the faceplate 404 a, 404 b. When an internal volume of a showerhead is reduced, providing a more uniform distribution of flow across a faceplate may necessitate an increase in the pressure drop between a plenum volume and a processing chamber. Generally, gas flows along a path of least resistance, so if the faceplate 404 b in the low volume showerhead 400 b has a low pressure drop, then the flow of gas would jet through the center of the faceplate 404 b. A higher pressure drop, however, would push the flow of gas more outwardly towards the edges of the faceplate 404 b. To facilitate a higher pressure drop, a number of through-holes in the faceplate 404 b may be decreased to accompany a reduced internal volume from the conventional showerhead 400 a to the low volume showerhead 400 a. Otherwise, if there is an excess number of through-holes in the faceplate 404 b, then the pressure drop may be too low and flux would be not be uniform across the faceplate 404 b from center to the edge. In some implementations, the number of through-holes in the faceplate 404 b in the low volume showerhead 400 b can be between about 1000 through-holes and about 3000 through-holes, or between about 1500 through-holes and about 2500 through-holes. For example, in Table 1, the conventional showerhead 400 a can be reduced from 3292 through-holes to 2257 through-holes in the low volume showerhead 400 b.

For a given flow rate of gas through the low volume showerhead 400 b, the number of through-holes in the faceplate 404 b can achieve a particular pressure drop and thereby provide a particular distribution of flow across the faceplate 404. If the flow rate of gas were low, then fewer through-holes would be necessary to achieve a desired uniformity of flow across the faceplate 404 b.

In some implementations, the arrangement of through-holes in the faceplate 404 a, 404 b can also influence the uniformity of flow across the faceplate 404 a, 404 b. In some implementations, geometric arrangement of the through-holes can be hexagonal. For example, the conventional showerhead 400 a can have a faceplate 404 a with a hexagonal arrangement of through-holes. In some implementations, the geometric arrangement of the through-holes can be triangular. For example, the low volume showerhead 400 b can have a faceplate 404 b with a triangular arrangement of through-holes.

The conventional showerhead 400 a can include a large, non-porous baffle 410 a centered underneath the stem 422 a to avoid or otherwise minimize the effects of jetting through the center of the faceplate 404 a. The large, non-porous baffle 410 a can have a diameter of 2.13 inches. The diameter of the non-porous baffle 410 a can be greater than a diameter of the expanded tube 426 a in the conventional showerhead 400 a. However, a volume of the plenum volume 430 a may be increased to accommodate the large, non-porous baffle 410 a underneath the stem 422 a for sufficient flow uniformity. The increased volume may be provided by a conical portion of the plenum volume 430 a so that the flow of gas may be distributed outwardly. The backplate 402 a may be sloped back to provide the conical portion of the plenum volume 430 a.

In contrast, the low volume showerhead 400 b of the present disclosure can include a small, porous baffle 410 b centered underneath the stem 422 b to avoid or otherwise minimize the effects of jetting through the center of the faceplate 404 b. In some implementations, the small, porous baffle 410 b can be substantially smaller than the large, non-porous baffle 410 a. The small, porous baffle 410 b can have a diameter between about 0.1 inches and about 2.0 inches. For example, the small, porous baffle 410 b can have a diameter of 0.79 inches. A diameter of the faceplate 404 b can be substantially larger than the diameter of the small, porous baffle 410 b. For example, the diameter of the faceplate 404 b can be 13 inches. In some implementations, the diameter of the faceplate 404 b can be at least four times greater than the diameter of the small, porous baffle 410 b, or at least ten times greater than the diameter of the small, porous baffle 410 b.

Typically, the reduction in the internal volume from the conventional showerhead 400 a to the low volume showerhead 400 b produces a “volume penalty” where the reduced internal volume adversely affects flow uniformity by reducing flow uniformity across the faceplate 404 b. To avoid this volume penalty in a low volume showerhead 400 b, the present disclosure can provide a small, porous baffle 410 b where the small, porous baffle 410 b can be positioned in a region 435 b between the plenum volume 430 b and the stem 422 b. The small, porous baffle 410 b can be positioned above the plenum volume 430 b without blocking the flow of gas. Instead, the small, porous baffle 410 b can be positioned in the region 435 b for improved flow uniformity, where the diameter of the small, porous baffle 410 b as well as the size, number, and arrangement of through-holes in the small, porous baffle 410 b can direct the flow of gas into the volume plenum 430 b, thereby influencing flow uniformity across the faceplate 404 b. In addition, the size, number, and arrangement of through-holes in the faceplate 404 b can be configured to achieve a higher pressure drop across the faceplate 404 b and obtain a desired flow uniformity. For example, a diameter of the through-holes in the small, porous baffle 410 b can be between about 0.01 inches and about 0.15 inches, such as about 0.08 inches. The small, porous baffle 410 b can include six holes arranged in a hexagonally-shaped ring, as illustrated in FIG. 5 and FIG. 7B. The six holes may be positioned closer towards the edge of the small, porous baffle 410 b than the center of the small, porous baffle 410 b. A diameter of the through-holes in the faceplate 404 b can be between about 0.01 inches and about 0.10 inches, such as about 0.04 inches. The faceplate 404 b can include over 2000 holes arranged in a plurality of triangular patterns, as illustrated in FIG. 5.

FIG. 5 shows an example layout of an arrangement of through-holes 532, 552 for a faceplate and through-holes 512 a porous baffle in a low volume showerhead. Through-holes 532 in a faceplate in a conventional showerhead can form a hexagonal arrangement 550, and through-holes 552 may be added to the through-holes 532 in a low volume showerhead to form a triangular arrangement 560. Through-holes 512 in a porous baffle may be positioned over through-holes 532 of the faceplate. The arrangement of through-holes 512 in a porous baffle and the arrangement of through-holes 532, 552 in a faceplate can influence the uniformity of flow across the faceplate.

FIG. 6A shows a side section view of a portion of an example showerhead including a baffle 610 a with arrows 640 a indicating nominal gas flow directions within the showerhead. FIG. 6B shows a side section view of a portion of an example low volume showerhead including a porous baffle 610 b with arrows 640 b indicating nominal gas flow directions within the low volume showerhead. Flow vectors 640 a for flow of gas from a gas inlet 620 a can be indicated by arrows in FIG. 6A, and flow vectors 640 b for flow of gas from a gas inlet 620 b can be indicated by arrows in FIG. 6B. The position, size, and porosity of the baffles 610 a, 610 b can influence the flow vectors 640 a, 640 b through the through-holes 632 a, 632 b of the faceplates 604 a, 604 b. The size, arrangement, and number of through-holes 612 b in the baffle 610 b can influence the flow vectors 640 b through the through-holes 632 b of the faceplate 604 b. In FIG. 6A, a baffle 610 a can direct the flow vectors 640 a outwardly towards the edges of a faceplate 604 a. However, in FIG. 6B, a porous baffle 610 b can direct the flow vectors 640 b outwardly towards the edges and towards the center of the faceplate 604 b, resulting in increased flux towards the center of the faceplate 604 b. In ALD applications, this can lead to a higher concentration of dose at the center of the substrate.

FIG. 7A shows an isometric view of an example baffle 710 a in a conventional showerhead 700 a. The conventional showerhead 700 a includes a backplate 702 a and a gas inlet 720 a fluidly coupled to a plenum volume of the conventional showerhead 700 a through the backplate 702 a. A baffle 710 a may be recessed in the plenum volume, where the baffle 710 a may be mounted from a side of the backplate 702 a via one or more internal support posts 714 a.

FIG. 7B shows an isometric view of an example baffle 710 b including a plurality of through-holes 712 b in a low volume showerhead 700 b. The low volume showerhead 700 b includes a backplate 702 b and a gas inlet 720 b fluidly coupled to a plenum volume of the low volume showerhead 700 b through the backplate 702 b. At an interface between the backplate 702 b and the gas inlet 720 b, a pocket or transition region 735 b is provided between the plenum volume and the gas inlet 720 b. In some implementations, a baffle 710 b may be recessed in the transition region 735 b or extending from the transition region 735 b, where the baffle 710 b may be mounted from the transition region 735 b via one or more internal support posts 714 b. The baffle 710 b may include a plurality of through-holes 712 b. In some implementations, the plurality of through-holes 712 b may be selectively arranged more towards the edges of the baffle 710 b than the center of the baffle 710 b. In some implementations, the porosity of the baffle 710 b can be between about 5% and about 25%, such as about 10%. In some implementations, the baffle 710 b can made of a porous material or the baffle 710 b can be made of a solid material with through-holes 712 b provided therethrough. In some implementations, the through-holes 712 b of the baffle 710 b may be arranged in a hexagonal pattern.

FIG. 8 shows a graph depicting axial flow velocity of gas from a faceplate of a showerhead as a function of a radial dimension of the faceplate. The axial flow velocity as measured 1 mm from a faceplate of a showerhead can reflect the uniformity of the flow of gas from the showerhead, where the axial flow velocity is graphically depicted from center to edge of the faceplate. At 5 standard liters per minute (slm) of oxygen and a pressure of 6 Torr, a showerhead without a baffle exhibits extremely fast axial flow velocity near the center of the faceplate and extremely slow axial flow velocity within a few millimeters of near the center of the faceplate. Without a baffle, the flow uniformity from center to edge of the faceplate is very poor. At 5 slm of oxygen and a pressure of 6 Torr, a showerhead with a non-porous baffle exhibits very slow axial flow velocity around the center of the faceplate and increased axial flow velocity closer towards the edge of the faceplate. With a non-porous baffle, the flow uniformity from center to edge of the faceplate is poor. With a porous baffle that is 2.5 mm from the surface of the showerhead and including six through-holes each being 0.08 inches in diameter, the axial flow velocity from the center to edge of the faceplate is relatively uniform. The porous baffle can be 2 cm in diameter and 1 mm thick, and the six through-holes can be centered at 1 cm apart.

FIG. 9 shows a graph depicting a percentage of film non-uniformity of atomic layer deposition for two showerheads. The film non-uniformity can be calculated by taking the difference between the thickest portion and the thinnest portion of the deposited film, and dividing that value by twice the mean of the thickness of the deposited film: % non-uniformity=(max−min)/(2*mean). In FIG. 9, the conventional showerhead can produce a produce a non-uniformity of about 0.5%, whereas the low volume showerhead of the present disclosure can yield a non-uniformity of about 0.2%. Thus, by designing the low volume showerhead of the present disclosure, film uniformity can be significantly improved in ALD processing.

The low volume showerhead of the present disclosure can provide a hardware configuration that can obtain film uniformity without having to compensate by adjusting various process steps or process knobs. In other words, by providing a low volume showerhead that is targeted towards improving film uniformity, the film uniformity may be decoupled from process parameters. As a result, film properties such as wet etch rate, and dry etch rate can be decoupled from the film uniformity. Additional film properties may include dielectric constant, refractive index, wet etch rate, dry etch rate, optical properties, porosity, density, composition, hardness and modulus, resist strip and ash rate, chemical mechanical planarization removal rate, and more.

Typically, obtaining a desirable level of film uniformity can be accomplished by adjusting various process parameters. In some implementations, process parameters such as flow rates, dose time, purge time, radio-frequency (RF) power, RF on time, and other process parameters can be tuned to achieve a desirable film uniformity. By way of an example, film uniformity can be improved by increasing processing times for each ALD cycle to provide greater saturation. However, throughput would be decreased. In another example, film uniformity can be improved by flowing more precursor (e.g., dose increase). However, increasing the precursor dose can lead to increased chemical cost, adverse effects on the stoichiometry on the film, and undesirable changes to film properties like wet etch rate and dry etch rate. Thus, typical approaches for obtaining a desirable level of film uniformity can undesirably impact throughput and film properties.

Table 2 compares the low volume showerhead of the present disclosure with process parameters of dose increase, RF power, and RF on time with respect to film uniformity (center thickness) and film properties (wet etch rate and dry etch rate).

TABLE 2 Center Wet Etch Dry Etch Thickness Rate Rate Low Volume Showerhead Increases No effect No effect Dose Increase Increases Increases Increases RF Power Decreases No effect Decreases RF On Time Decreases Decreases No effect

As shown in Table 2, the low volume showerhead of the present disclosure increases the center thickness of the deposited film without affecting the wet etch rate and the dry etch rate of the deposited film. However, adjusting process parameters such as dose level, RF power, and RF on time does not decouple the film uniformity from the film properties. Increasing the dose increases the wet etch rate and the dry etch rate of the deposited film. Decreasing the RF power decreases the dry etch rate of the deposited film, and decreasing the RF on time decreases the wet etch rate of the deposited film. Hence, providing the low volume showerhead can provide a wider process window for semiconductor processing while obtaining a desirable level of film uniformity without having to fine-tune process parameters like flow rates, dose time, purge time, etc. to obtain the desirable level of film uniformity. In some implementations, the low volume showerhead can achieve a film non-uniformity of less than about 1.0%, such as less than about 0.5% or less than about 0.3%. In some implementations, a film non-uniformity of less than about 1.0% can be achieved with an ALD cycle of 1.5 seconds or less. For example, the dose time can be 0.4 seconds or less, the purge time can be 0.4 seconds or less, and plasma step can be 0.4 seconds or less, and the post-plasma purge step can be 0.15 seconds or less. In contrast, an ALD cycle in a conventional showerhead can be greater than about 1.5 seconds per cycle, with a dose time being 0.6 seconds or more, the purge time being 0.4 seconds or more, the plasma step being 0.4 seconds or more, and the post-plasma purge step being 0.15 seconds or more. The low volume showerhead can increase throughput by reducing the total time for an ALD cycle while obtaining a desirable level of film uniformity. Moreover, the low volume showerhead can obtain the desirable level of film uniformity without affecting other film properties, such as wet etch rate and dry etch rate.

A low volume showerhead of the present disclosure may be installed in a semiconductor process chamber. A process chamber can include a low volume showerhead that is mounted to the top of a chamber housing. A substrate support may support a semiconductor substrate within the process chamber and beneath the low volume showerhead. A microvolume may be formed between the substrate support and the low volume showerhead. The microvolume may serve as a substrate reaction area and may help concentrate and retain process gases in the vicinity of the semiconductor substrate during processing. The substrate support may be configured to move up and down to facilitate loading and unloading operations. In some implementations, the low volume showerhead may be suspended from a lid of the process chamber by a stem and may not itself form part of the “lid” of the process chamber. In such implementations, the low volume showerhead may be configured to move up and down to facilitate substrate loading and unloading operations.

In some implementations, one or more process chambers may be provided as process stations in a multi-station semiconductor processing too. In some implementations, a single process chamber may include multiple processing stations, some or all of which may have their own low volume showerhead assemblies.

FIG. 10 shows a schematic view of a multi-station processing tool that may include a low volume showerhead with a porous baffle. The multi-station processing tool 1000 may include an inbound load lock 1002 and an outbound load lock 1004. A robot 1006, at atmospheric pressure, can be configured to move substrates from a cassette loaded through a pod 1008 into inbound load lock 1002 via an atmospheric port 1010. A substrate may be placed by the robot 1006 on a pedestal 1012 in the inbound load lock 1002, the atmospheric port 1010 may be closed, and the load lock may then be pumped down. If the inbound load lock 1002 includes a remote plasma source, the substrate may be exposed to a remote plasma treatment in the load lock prior to being introduced into a processing chamber 1014. Further, the substrate also may be heated in the inbound load lock 1002, for example, to remove moisture and adsorbed gases. Next, a chamber transport port 1016 to processing chamber 1014 may be opened, and another robot (not shown) may place the substrate into the processing chamber 1014 on a pedestal of a first station shown in the reactor for processing. While the implementation depicted in FIG. 10 includes load locks, it will be appreciated that, in some implementations, direct entry of a substrate into a process station may be provided.

The depicted processing chamber 1014 includes four process stations, numbered from 1 to 4 in the implementation shown in FIG. 10. Each station may have a heated or unheated pedestal (shown at 1018 for station 1), and gas line inlets. It will be appreciated that in some implementations, each process station may have different or multiple purposes. For example, in some implementations, a process station may be switchable between an ALD and plasma-enhanced chemical vapor deposition (PECVD) process mode. Additionally or alternatively, in some implementations, processing chamber 1014 may include one or more matched pairs of ALD and PECVD process stations. While the depicted processing chamber 1014 comprises four stations, it will be understood that a processing chamber according to the present disclosure may have any suitable number of stations. For example, in some implementations, a processing chamber may have five or more stations, while in other implementations a processing chamber may have three or fewer stations.

Each station may include a separate showerhead assembly that delivers process gases to a substrate at the associated station. In some implementations, some or all of these showerheads may utilize a low volume showerhead with a porous baffle as described herein. For example, if a station provides ALD processing, or other processing that may benefit from use of the equipment described herein, to a substrate, the showerhead for that station may be a low volume showerhead with a porous baffle as discussed herein.

FIG. 10 also depicts a substrate handling system 1090 for transferring substrates within processing chamber 1014. In some implementations, substrate handling system 1090 may transfer substrates between various process stations and/or between a process station and a load lock. It will be appreciated that any suitable substrate handling system may be employed. Non-limiting examples include substrate carousels and substrate handling robots. FIG. 10 also depicts a system controller 1050 employed to control process conditions and hardware states of process tool 1000. System controller 1050 may include one or more memory devices 1056, one or more mass storage devices 1054, and one or more processors 1052. Processor 1052 may include a CPU or computer, analog and/or digital input/output connections, stepper motor controller boards, etc.

In some implementations, a controller 1050 is part of a system, which may be part of the above-described examples. Such systems can comprise semiconductor processing equipment, including a processing tool or tools, chamber or chambers, a platform or platforms for processing, and/or specific processing components (a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing of a semiconductor wafer or substrate. The electronics may be referred to as the “controller,” which may control various components or subparts of the system or systems. The controller 1050, depending on the processing requirements and/or the type of system, may be programmed to control any of the processes disclosed herein, including the delivery of processing gases, temperature settings (e.g., heating and/or cooling), pressure settings, vacuum settings, power settings, radio frequency (RF) generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, positional and operation settings, wafer transfers into and out of a tool and other transfer tools and/or load locks connected to or interfaced with a specific system.

Broadly speaking, the controller 1050 may be defined as electronics having various integrated circuits, logic, memory, and/or software that receive instructions, issue instructions, control operation, enable cleaning operations, enable endpoint measurements, and the like. The integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and/or one or more microprocessors, or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files), defining operational parameters for carrying out a particular process on or for a semiconductor substrate or to a system. The operational parameters may, in some embodiments, be part of a recipe defined by process engineers to accomplish one or more processing steps during the fabrication of one or more layers, materials, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and/or dies of a substrate.

The controller 1050, in some implementations, may be a part of or coupled to a computer that is integrated with, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller 1050 may be in the “cloud” or all or a part of a fab host computer system, which can allow for remote access of the substrate processing. The computer may enable remote access to the system to monitor current progress of fabrication operations, examine a history of past fabrication operations, examine trends or performance metrics from a plurality of fabrication operations, to change parameters of current processing, to set processing steps to follow a current processing, or to start a new process. In some examples, a remote computer (e.g. a server) can provide process recipes to a system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and/or settings, which are then communicated to the system from the remote computer. In some examples, the controller receives instructions in the form of data, which specify parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller 1050 is configured to interface with or control. Thus as described above, the controller 1050 may be distributed, such as by comprising one or more discrete controllers that are networked together and working towards a common purpose, such as the processes and controls described herein. An example of a distributed controller 1050 for such purposes would be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber.

Without limitation, example systems may include a plasma etch chamber or module, a deposition chamber or module, a spin-rinse chamber or module, a metal plating chamber or module, a clean chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing systems that may be associated or used in the fabrication and/or manufacturing of semiconductor substrate.

As noted above, depending on the process step or steps to be performed by the tool, the controller 1050 might communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout a factory, a main computer, another controller, or tools used in material transport that bring containers of substrates to and from tool locations and/or load ports in a semiconductor manufacturing factory.

In some implementations, system controller 1050 controls all of the activities of process tool 1000. System controller 1050 executes system control software 1058 stored in mass storage device 1054, loaded into memory device 1056, and executed on processor 1052. System control software 1058 may include instructions for controlling the timing, mixture of gases, chamber and/or station pressure, chamber and/or station temperature, substrate temperature, target power levels, RF power levels, substrate pedestal, chuck and/or susceptor position, and other parameters of a particular process performed by process tool 1000. System control software 1058 may be configured in any suitable way. For example, various process tool component subroutines or control objects may be written to control operation of the process tool components necessary to carry out various process tool processes. System control software 1058 may be coded in any suitable computer readable programming language.

In some implementations, system control software 1058 may include input/output control (IOC) sequencing instructions for controlling the various parameters described above. For example, each phase of an ALD process may include one or more instructions for execution by system controller 1050. The instructions for setting process conditions for an ALD process phase may be included in a corresponding ALD recipe phase. In some implementations, multiple showerheads, if present, may be controlled independently to allow for separate, parallel process operations to be performed.

Other computer software and/or programs stored on mass storage device 1054 and/or memory device 1056 associated with system controller 1050 may be employed in some implementations. Examples of programs or sections of programs for this purpose include a substrate positioning program, a process gas control program, a pressure control program, a heater control program, and a plasma control program.

A substrate positioning program may include program code for process tool components that are used to load the substrate onto pedestal 1018 and to control the spacing between the substrate and other parts of process tool 1000.

A process gas control program may include code for controlling gas composition and flow rates and optionally for flowing gas into one or more process stations prior to deposition in order to stabilize the pressure in the process station. A pressure control program may include code for controlling the pressure in the process station by regulating, for example, a throttle valve in the exhaust system of the process station or a gas flow into the process station.

A heater control program may include code for controlling the current to a heating unit that is used to heat the substrate. Alternatively, the heater control program may control delivery of a heat transfer gas (such as helium) to the substrate.

A plasma control program may include code for setting RF power levels applied to the process electrodes in one or more process stations. The plasma control program may, in appropriate situations, include code for controlling an external plasma generator and/or valving required to supply process gas to a plasma generator or radical source volume.

In some implementations, there may be a user interface associated with system controller 1050. The user interface may include a display screen, graphical software displays of the apparatus and/or process conditions, and user input devices such as pointing devices, keyboards, touch screens, microphones, etc.

In some implementations, parameters adjusted by system controller 1050 may relate to process conditions. Non-limiting examples include process gas composition and flow rates, temperature, pressure, plasma conditions (such as RF bias power levels), pressure, temperature, etc. These parameters may be provided to the user in the form of a recipe, which may be entered utilizing the user interface.

Signals for monitoring the process may be provided by analog and/or digital input connections of system controller 1050 from various process tool sensors. The signals for controlling the process may be output on the analog and digital output connections of process tool 1000. Non-limiting examples of process tool sensors that may be monitored include mass flow controllers, pressure sensors (such as manometers), thermocouples, etc. Appropriately-programmed feedback and control algorithms may be used with data from these sensors to maintain process conditions.

The system controller 1050 may provide program instructions for implementing various semiconductor fabrication processes. The program instructions may control a variety of process parameters, such as DC power level, RF bias power level, pressure, temperature, etc. The instructions may control the parameters to operate in-situ deposition of film stacks.

A system controller may typically include one or more memory devices and one or more processors configured to execute the instructions so that the apparatus will perform a method in accordance with the present invention. Machine-readable media containing instructions for controlling process operations in accordance with the present invention may be coupled to the system controller.

While the semiconductor processing tool shown in FIG. 10 depicts a single, four-station process chamber, or module, other implementations of semiconductor processing tools may include multiple modules, each with a single station or multiple stations. Such modules may be interconnected with one another and/or arranged about one or more transfer chambers that may facilitate movement of substrates between the modules. One or more of the stations provided by such multi-module semiconductor processing tools may be equipped with low volume showerheads including porous baffles, as described herein, as needed.

Generally speaking, a low volume showerhead including a porous baffle as described herein may be mounted in a reaction chamber above a substrate support configured to support one or more semiconductor substrates. The low volume showerhead may, for example, also serve as a lid, or part of a lid, for the reaction chamber. In other implementations, the low volume showerhead may be a “chandelier” type showerhead and may be suspended from the lid of the reaction chamber by a stem or other support structure.

The apparatus/process described hereinabove may be used in conjunction with lithographic patterning tools or processes, e.g., steppers, for example, for the fabrication or manufacture of semiconductor devices, displays, LEDs, photovoltaic panels and the like. Typically, though not necessarily, such tools/processes will be used or conducted together in a common fabrication facility. Lithographic patterning of a film typically comprises some or all of the following steps, each step enabled with a number of possible tools: (1) application of photoresist on a workpiece, i.e., wafer, using a spin-on or spray-on tool; (2) curing of photoresist using a hot plate or furnace or UV curing tool; (3) exposing the photoresist to visible or UV or x-ray light with a tool such as a wafer stepper; (4) developing the resist so as to selectively remove resist and thereby pattern it using a tool such as a wet bench; (5) transferring the resist pattern into an underlying film or workpiece by using a dry or plasma-assisted etching tool; and (6) removing the resist using a tool such as an RF or microwave plasma resist stripper.

Although the foregoing has been described in some detail for purposes of clarity and understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. It should be noted that there are many alternative ways of implementing the processes, systems, and apparatus described. Accordingly, the described embodiments are to be considered as illustrative and not restrictive. 

What is claimed is:
 1. A showerhead for use in a semiconductor processing apparatus, the showerhead comprising: a plenum volume having a first surface and a second surface opposite the first surface, the first surface and the second surface at least partially defining the plenum volume of the showerhead; a faceplate including a plurality of first through-holes, the plurality of first through-holes extending from a first side to a second side of the faceplate, the first side of the faceplate defining the first surface of the plenum volume; a backplate opposite the faceplate; wherein a side of the backplate defines a second surface of the plenum volume; a stem connected to the backplate and in fluid communication with the plenum volume; and a baffle plate including a plurality of second through-holes, the baffle plate being positioned at least partially within or fully within a region between the plenum volume and the stem, wherein the region is recessed into the side of the backplate and is in direct fluid communication with the plenum volume and direct fluid communication with the stem.
 2. The showerhead of claim 1, wherein a diameter of the faceplate is at least four times greater than a diameter of the baffle plate.
 3. The showerhead of claim 2, wherein the diameter of the faceplate is at least ten times greater than the diameter of the baffle plate.
 4. The showerhead of claim 1, further comprising: one or more gas inlets in the stem configured to deliver gas to the plenum volume, wherein the baffle plate is mounted in the recessed region below the one or more gas inlets and above the plenum volume.
 5. The showerhead of claim 1, wherein a volume of the stem is between about 1 milliliter and about 50 milliliters.
 6. The showerhead of claim 1, wherein each of the stem, the recessed region, and the plenum volume defines a cylindrical volume, and wherein a diameter of the plenum volume is greater than a diameter of the recessed region, and the diameter of the recessed region is greater than a diameter of the stem.
 7. The showerhead of claim 1, wherein a volume of the showerhead is between about 50 milliliters and about 500 milliliters.
 8. The showerhead of claim 7, wherein the volume of the showerhead is between about 100 milliliters and about 300 milliliters.
 9. The showerhead of claim 1, wherein a porosity of the baffle plate is between about 5% and about 25%.
 10. The showerhead of claim 1, wherein the plurality of second through-holes are positioned more towards the edges of the baffle plate than the center of the baffle plate.
 11. The showerhead of claim 1, wherein the baffle plate is substantially centered on the stem and substantially parallel to the first surface and the second surface.
 12. The showerhead of claim 1, wherein a number of first through-holes is between about 1500 and about 2500 through-holes.
 13. The showerhead of claim 1, wherein the plurality of first through-holes are arranged in a triangular arrangement on the faceplate and the second through-holes are arranged in a hexagonal arrangement on the baffle plate.
 14. A semiconductor processing station, the semiconductor processing station including the showerhead of claim
 1. 15. The semiconductor processing station of claim 14, further comprising: a controller configured with instructions to perform the following operations: providing a substrate into the semiconductor processing station; introducing reactant gas into the semiconductor processing station through the showerhead to adsorb onto the surface of the substrate; introducing a purge gas into the semiconductor processing station through the showerhead; and applying a plasma to form a thin film layer from the adsorbed reactant gas on the surface of the substrate.
 16. The semiconductor processing station of claim 15, wherein a film non-uniformity of the thin film layer is less than about 0.5%.
 17. The semiconductor processing station of claim 16, wherein the film non-uniformity is decoupled from one or more process parameters associated with one or more of introducing the gas reactant, introducing the purge gas, and applying the plasma.
 18. The semiconductor processing station of claim 15, wherein forming the thin film layer in an atomic layer deposition (ALD) cycle is performed in less than about 1.5 seconds.
 19. A semiconductor processing tool, the semiconductor processing tool including the semiconductor processing station of claim
 15. 20. The semiconductor processing tool of claim 19, wherein the semiconductor processing tool includes a stepper. 